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Re: XFS reports lchmod failure, but changes file system contents
- From: "Darrick J. Wong" <darrick dot wong at oracle dot com>
- To: Christoph Hellwig <hch at infradead dot org>
- Cc: Florian Weimer <fw at deneb dot enyo dot de>, linux-xfs at vger dot kernel dot org, libc-alpha at sourceware dot org, linux-fsdevel at vger dot kernel dot org, viro at zeniv dot linux dot org dot uk
- Date: Wed, 12 Feb 2020 10:37:18 -0800
- Subject: Re: XFS reports lchmod failure, but changes file system contents
- References: <874kvwowke.fsf@mid.deneb.enyo.de> <20200212161604.GP6870@magnolia> <20200212181128.GA31394@infradead.org>
On Wed, Feb 12, 2020 at 10:11:28AM -0800, Christoph Hellwig wrote:
> On Wed, Feb 12, 2020 at 08:16:04AM -0800, Darrick J. Wong wrote:
> > xfs_setattr_nonsize calls posix_acl_chmod which returns EOPNOTSUPP
> > because the xfs symlink inode_operations do not include a ->set_acl
> > pointer.
> >
> > I /think/ that posix_acl_chmod code exists to enforce that the file mode
> > reflects any acl that might be set on the inode, but in this case the
> > inode is a symbolic link.
> >
> > I don't remember off the top of my head if ACLs are supposed to apply to
> > symlinks, but what do you think about adding get_acl/set_acl pointers to
> > xfs_symlink_inode_operations and xfs_inline_symlink_inode_operations ?
>
> Symlinks don't have permissions or ACLs, so adding them makes no
> sense.
Ahh, I thought so!
> xfs doesn't seem all that different from the other file systems,
> so I suspect you'll also see it with other on-disk file systems.
Yeah, I noticed that btrfs seems to exhibit the same behavior.
I also noticed that ext4 actually /does/ implement [gs]et_acl for
symlinks.
> We probably need a check high up in the chmod and co code to reject
> the operation early for O_PATH file descriptors pointing to symlinks.
<nod>
--D